1. Field of Invention
The present invention relates to gas filter devices, particularly gas filter devices of the type that utilize a barrier for removal of particulate contaminates.
2. Description of the Prior Art
Filter devices adapted to be placed in an oxygen supply line for use in hospitals or other medical environments in the treatment of various patient systems are well known. Typically, such a filter includes a filter membrane stretched across a housing, the membrane adapted to entrap any suspended particulate matter.
It is also common that the housing of the filter devices of the prior art be separated into two generally dome-shaped or concavely-shaped halves, each half having a hub for connection to an oxygen line. Typically, the two halves are chemically bonded or mechanically joined together, mounting the filter membrane therebetween.
In a blood filter, a continuous circumferential seal between the two housings has been made by use of ultrasonic welding techniques. In U.S. Pat. No. 4,157,967 to Meyst et al, a plurality of filter pads are placed between two housings. The filter pads are joined together at the circumference thereof by heat sealing. The pad is placed between a pair of housings which grasp the pad therebetween. One of the housings has an annular plastic ridge which rests on a flange of the other housing. The sonic energy melts the ridge around the entire circumference of the filter device, forming a seal between the two housings so that the filter may be used for liquids, like blood.
In Gangemi (U.S. Pat. No. 4,159,954) an isolator filter is shown of the same general two-housing construction supporting a filter membrane therebetween. Each housing has a pair of circumferential ribs adapted to align with a like pair of circumferential ribs on the other housing to hold the filter membrane therebetween. The ribs are actually sonically welded to the filter membrane.
It has not heretofore been known to utilize a low energy weld bead or rib, to join the two housings of a filter device directly together. The Meyst patent does weld the two housings together, but requires sufficient time for application of energy to melt a relatively massive flange. The Gangemi patent does utilize ribs that can concentrate sonic energy and therefore be easily melted, but does not directly weld the housings to each other in a desirable hermetic seal.